Luminescent behavior of two novel thermo-sensitive poly(N-isopropylacrylamide) hydrogels incorporated with rare earth complexes

Two novel luminescent temperature-sensitive poly(N-isopropylacrylamide) hydrogels fabricated with rare earth (Eu, Tb) picolinic acid complexes were in-situ synthesized within the interpenetration networks. Fluorescence spectra indicate the two functional gels exhibit red for Eu3+ species and green emissions for Tb3+ ones, respectively, whose luminescence intensities are changed due to temperature increasing from 5 to 30 degrees C until totally quenched at lower critical solution temperature (33 degrees C). In addition, the decreasing luminescence behavior obeys the simple linear equations. The releasing experiment substantiates that there may be complexation between O=C-NH- moieties of P-NIPAA and Eu3+ ions for the prolonged released time.